Did you completely remove Norton using removal tool before you installed AVG?
If you have trial version installed you are entitled for the full support here:
Otherwise, CPU usage could have been caused by caching of the files or due to conflict with other software.
Please try to disable cache server:
Tools - Advanced settings - Cache server - Untick caching enabled.
If that does not help, provide us with list of programs that are running in background.
I am a Norton user, or have been for quite a few years now. I was looking to change as liveupdate decides to pop up whenever it wants, sometimes even when disabled. All the little norton popups are about as annoying as having a virus.
Anyway, I decided to try AVG 2011 30 day free trial. I like the interface at first and it seemed to be a nice change.
Then I go to game online, which is mainly what I do with my PCs. When I load my games, AVG starts using 100% of my HDD. It is in game mode. When the PC is simply idling, it uses about 6% of my CPU and the HDD jumps all over the place. Around 30% is probably average. I even killed all its processes in the task manager and still it was sucking up resources.
This isnt a rant thread, and if anyone has some tips on how to stop the resource hogging, it'd be nice. As of right now, my opinion is that it is a piece of junk.